Re: [LAD] MIDI SysEx "7 (Signed)" - Linux-audio-dev

12 Sep 2013

On Thu, 2013-09-12 at 14:22 +0200, Alexandre Ratchov wrote:
...
  On Mon, Sep 09, 2013 at 04:45:53PM +0200, Ralf Mardorf
wrote:
  Hi,

 I'm writing a CLI editor for the Matrix-1000. Regarding to the owner's
 manual some parameters have 6 bit values, so I gave them a range from 0
 to 63, for the 7 bit value I definite a range from 0 to 127. Many values
 are described as "7 (Signed)". I consider those values should get a
 range from -64 to 0 to +63, IOW I understand it as a two's complement,
 but the editor of my Atari ST's Cubase 3.1 doesn't give them a value
 from -64 to 0 to +63, instead the GUI's value range is from 0 to 127.  
 I don't have a matrix-1000, but there's plenty of midi gears that
 use biased 7-bit integers instead of signed two complement. I mean:

 0   -> min value
 64  -> neutral value
 127 -> maximum value

 example, a value in the [-0.5:0.5] range would be represented
 with the 7-bit number in 1/128 steps as follows:

 0   -> -64/128
 1   -> -63/128
 ...
 64  -> 0
 65  -> 1/128
 ...
 127 -> 63/128

 note that 0.5 cannot be reached with this scheme; so sometimes only
 the range 1..127 of the 7-bit number is used in 1/127 steps.

 HTH 
Thank you Alexandre,

at the moment it's possible to use -64 to +63 by signed two complement
and it's also possible to continue up to +127, assumed the two
complement should cause audible value "jumps".
I simply will connect the Matrix-1000 and then test what happens.

I found a free Windows editor that does provide -63 to +63 (no 0.5
steps) but since I run Windows in VBox, I don't know if I could get a
MIDI output to take a look at the SysEx data.

Another issue are some bit switches, e.g. for a DCO Waveform enable
bit 0 = pulse, 1 = wave and 2 = noise. For the Windows editor it's
possible to turn on pulse, wave and noise at the same time, while I
suspected that if one is turned on, the others should be turned off. 

However, I will test it using the editor I've written, with the Matrix I
own.

I hoped somebody who owns a Matrix too does know, too avoid those tests
when I started writing.

If there should be the need to rewrite what already is written, it
wouldn't cause work, the actual work is to copy all parameters from the
manual and to find a way to make the Matrix's matrix clear for the
command line (without a GUI).
It's just a bash script using amidi, from the fact that I need to copy
all parameters from the manual and need to find a way to make the
Matrix's matrix clear without a GUI, the script is finished, so I easily
can test the behavior, whenever I've got some time to do it ;).

Regards,
Ralf